The human anatomy includes many types of tissues that can either voluntarily or involuntarily, perform certain functions. After disease, injury, or natural defects, certain tissues may no longer operate within general anatomical norms. For example, organs such as the heart may begin to experience certain failures or deficiencies. Some of these failures or deficiencies can be diagnosed, corrected or treated with implantable medical devices.
Implantable medical electrical leads are used with a wide variety of these implantable medical devices. For example, in the field of cardiac stimulation and monitoring, implantable leads are used with an implantable pulse generator (IPG), or implantable cardioverter/defibrillator (ICD), or a subcutaneous implantable cardioverter defibrillator (SubQ ICD). Implantable medical leads may be configured to allow electrodes to be positioned at desired cardiac locations so that the device can monitor and/or deliver stimulation therapy to the desired locations.
Implantable medical leads are also used with other types of therapy delivery devices to provide, as examples, neurostimulation, muscular stimulation, or gastric stimulation to target patient tissue locations via electrodes on the leads and located within or proximate to the target tissue. As one example, implantable leads may be positioned proximate to the vagal nerve for delivery of neurostimulation to the vagal nerve. Additionally, implantable leads may be used by medical devices for patient sensing and, in some cases, for both sensing and stimulation. For example, electrodes on implantable leads may detect electrical signals within a patient, such as an electrocardiogram, in addition to delivering electrical stimulation.
Currently, ICD's use endocardial or epicardial leads which extend from the ICD housing through the venous system to the heart. Electrodes positioned in or adjacent to the heart by the leads are used for pacing and sensing functions. Cardioversion and defibrillation shocks are generally applied between a coil electrode carried by one of the leads and the ICD housing, which acts as an active can electrode.
A SubQ ICD differs from the more commonly used ICD's in that the housing and leads are typically implanted subcutaneously such that the sensing and therapy are accomplished subcutaneously. The SubQ ICD does not require leads to be placed in the bloodstream. Instead, the SubQ ICD makes use of one or more electrodes on the housing, together with a subcutaneous lead that carries a defibrillation coil electrode and a sensing electrode.
The absence of endocardial or epicardial electrodes presents a challenge to determining a lead fault of the SubQ ICD. As described herein, the present disclosure addresses the need in art to provide mechanisms for performing a lead impedance measurement for a SubQ ICD.